All volcanoes erupt, but not always in the same way. There are seven types of volcanic eruptions: Strombolian, Vulcanian, Pelean, Hawaiian, Phreatic, Plinian and Subglacial.
A Strombolian eruption is named after a town in Sicily.
A Strombolian eruption, named after Stromboli in Sicily, consists of large bubbles of magma thrown tens to hundreds of meters into the air, until they fall to the ground and produce short, viscous flows of lava. Strombolian volcanic eruptions are caused by the buildup of bubbles, called gas slugs, that quickly rise to the surface, emerging with such force that they eject many tons of magma into the air. Strombolian eruptions are of low or medium intensity.
Volcanic eruptions are divided into seven categories.
Volcanic eruptions, named after Vulcano, a volcanic island in the Mediterranean, are characterized by large amounts of gas explosively released. Vulcanian eruptions are often accompanied by phreatic eruptions, or steam eruptions, caused when red-hot magma becomes constant with groundwater and instantly turns it into steam. In volcanic eruptions, a large cloud of volcanic ash forms in the sky above the volcano, with smoky white ash constituting the highest part of the smoke pillar. Volcanic volcanic eruptions usually don’t eject much magma into the air.
Composite volcanoes release lava and rock when they erupt.
The Pelean eruptions, also called “bright cloud” eruptions, are named after Mt. Pelee in the Caribbean. Peléan eruptions are characterized by sudden explosions of fragments of gas, dust, ash, and lava that rain down on miles-long areas in a pyroclastic avalanche. When a Pelean eruption occurs in a populated area, it can cause many deaths. Peléan’s volcanic eruptions are often accompanied by the creation of a lava dome.
Some volcanic eruptions eject ash into the stratosphere.
The Hawaiian eruptions are named after the eruptions of the Mauna Loa volcano in the Hawaiian Islands. These are among the most peaceful eruptions and can last for many years. They consist of large amounts of low-viscosity lava running down the slope of the volcano and produce very little volcanic ash or gas. A Hawaiian eruption is safe enough to be seen up close, and many Hawaii helicopter tours offer tours of the volcanic Mauna Loa. Over geological time, eruptions in Hawaii produce very large mountains, as is the case with the island of Hawaii itself – if measured from the ocean floor, Mauna Loa can be considered the tallest mountain on Earth.
Phreatic eruptions, also known as steam blast eruptions, are named after a word that means “well” or “spring” in Greek and refers to the contact of superheated magma with an underground water table. Phreatic eruptions result in explosions of steam, water, ash, rock and volcanic bombs, and are known to kill hundreds of people, mainly due to the release of toxic gases like carbon dioxide or hydrogen sulfide. The former only causes suffocation, while the latter is actually an active poison, killing plants and animals.
Plinian Eruptions, named after Pliny the Younger, whose uncle was killed in the Plinian eruption of Mt. Vesuvius in 79 CE, is the most severe and extreme of the volcanic eruptions. They consist of an extremely tall column of ash and magma being ejected all the way into the stratosphere (>11 km, 6.8 mi). This column spreads across the top, resembling a stone pine. Plinian volcanic eruptions are known to distribute dust over areas hundreds of kilometers wide and are often accompanied by very loud explosive noises that can be heard thousands of kilometers away. Plinian eruptions sometimes eject so much magma that the top of the volcano collapses, forming a caldera.
Subglacial volcanic eruptions occur when a volcano erupts beneath a layer of ice, which is usually more than a kilometer deep. Only five subglacial eruptions have been recorded in modern history, and only the most severe are capable of actually melting across the entire ice cap above.